The present invention relates to the formation of images by means of ultrasounds.
It relates more particularly to the formation of internal images of objects, optically opaque, through ultrasonic echography.
A device according to the invention provides the formation, instantaneously and continuously, of visible representations of the section of a heterogeous body having discontinuities, even mobile.
Such a device is particularly adapted to medical applications, as it provides the possibility of observing internal anatomic structures of a living being without discernible disturbances.
Of course, the ultrasonic echography device according to the invention has other applications than in the medical observation field, but it is for this application where the requirements are the most exacting that the device is particularly appropriate.
There is already known ultrasonic echography devices for the formation of images of internal objects, optically opaque.
Said devices differ between themselves substantially by their shape and the operating principle of the ultrasonic captor.
The apparatus with parallel beam plane probe comprise an ultrasonic transmitter-receiver formed of one or two series of elementary transducers positioned side by side, each elementary transducer converting the received electric energy into transmitted ultrasonic vibrations and/or converting the receive ultrasonic energy into a variable electric voltage, and a switching unit supplying in succession and cyclically the various transducers with electric pulses from a pulse generator in order to provide transmission of the ultrasonic pulses from the transducers, and which switches off the electric signals resulting from the conversion of ultrasonic echos sent back by the observed object and picked up by the transducers, in succession and cyclically, towards signal processing means supplying a visualizing device.
The sectorial analysis of a section may be obtained by means of a small dimension transmitter-receiver vibrating mechanically, or by means of a stationary transmitter-receiver generating an analysis beam reflected by a vibrating mirror, either through an array of transducers energized according to programmed sequences so that the ultrasonic beam, focused, has a variable direction and that the analysis area be sectorial.
The prior devices using non focused beam probes, use diverging ultrasound beams since there is no diffraction compensation. The section of each analysis beam increases as the distance from the transmitting transducer increases. Two reflecting objects therefore, of a section inferior to that of the analysis beam, are not differentiated. The smallest section which the system can form determines the system definition.
The object of the invention is to provide, by means of a very simple construction, similar performances to that of the prior devices, while extending the medical applications of said devices through a diminution of the area of the surface of the human body through which pass the ultrasounds.
The prior apparatus, with a flat probe, comprise actually either a simple unit supplying images of very insufficient definition (from about 6 mm to 10 mm), or a very complex unit piloted in certain cases by a powerful computer forming images having a definition near the theoretical value of half the wave length of the ultrasounds used.
In both cases, the total surface of the probe in contact with the biological milieu is important (10 cm.sup.2 about).
The contact area of the probes acting through a sectorial mechanical scanning is more reduced than previously; however, this advantage is largely offset by the disadvantages inherent the mechanical systems (wear, vibrations, slow cadence).